The resonant frequency and impedance of a chip antenna housed in a cellular phone or other small portable terminal changes due to the effects of the housing, the various electrical components mounted in the vicinity, and the structure of the substrate. Adjusting the impedance and resonant frequency of this type of chip antenna is therefore necessary for each small portable terminal model.
In, e.g., Japanese Laid-open Patent Application No. 2007-67993, a method is proposed in which the resonant frequency is adjusted by changing the length of an adjusting element provided on the base. According to this method, the resonant frequency can be adjusted without trimming the conductor pattern on the antenna block, and therefore chip antennas having the same structure can be used in a plurality of small portable terminal models, and components can be shared.
In Japanese Laid-open Patent Application No. 10-256825, a method is proposed in which the resonant frequency and impedance are adjusted by trimming the antenna electrode. According to this method, not just the resonant frequency but the impedance of the antenna can be adjusted.